(AP) -- The use of high-tech diagnostic imaging in emergency rooms has quadrupled since the mid-1990s, according to a new government report released Wednesday.
MRI, CT or PET scans were done or ordered in 14 percent of ER visits in 2007, the report from the Centers for Disease Control and Prevention found. That's four times as often as in 1996.
The frequency of the medical scans nearly tripled at doctor offices and outpatient clinics, to about 3 percent.
There are more and better scanning machines available today than in the 1990s, the report's authors noted. The scans provide a much clearer picture of problems inside the body than was available in the past, experts said.
But health officials and others worry about the safety and cost of all that scanning.
"I wish I had an answer as to whether that's great news or bad news," Dr. Rita Redberg, a cardiologist at the University of California, San Francisco, said of the increased use. Redberg, who has written about safety concerns of using CT scans, called the new statistics "astounding."
Without firm guidelines as to when the scans are medically necessary, it's hard to say whether the increased use is excessive, Redberg and others said.
The CDC's National Center for Health Statistics reported the numbers in its annual summary of U.S. data on disease conditions, health behaviors and use of medical services. The scan figures are based on visits to roughly 500 hospitals and 3,000 doctor's offices and outpatient clinics.
Researchers counted three kinds of scans: MRIs, or magnetic resonance imaging, which use powerful magnets and radio waves, CT scans, or computed tomography, which combine X-rays with sophisticated computers, and PET scans, or positron-emission tomography, which use X-rays and a radioactive substance.
Doctors started using the devices in the 1970s but the technology has dramatically improved, said Amy Bernstein, director of the team who put together the CDC report.
The number of machines has grown, too. In 2006, there were nearly 8,000 MRI machines, twice as many as in 1995, the CDC reported. The number of CT scanners jumped 20 percent in three years, to more than 10,100 in 2006.
The scans are expensive - a single CT scan can cost $500 to $1,000, and MRIs and PET scans can be much more expensive. The federal Medicare program has been trying to hold down imaging costs since its annual bill reached $12 billion.
Studies have not yet clearly demonstrated that the scans are lowering death rates, said Redberg, who is editor of the Archives of Internal Medicine.
"There's a question of whether we're getting our money's worth," said Dr. Linda Fried, dean of Columbia University's Mailman School of Public Health, in New York.
There also is concern about radiation from CT and PET scanners. Each CT scan is equivalent to 30 to 442 chest X-rays, and one recent study in her medical journal suggested that the CT scans ordered by doctors each year could lead to thousands of added cancer deaths in the decades to come, Redberg noted.
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More information: CDC report: http://www.cdc.gov/nchs